A conventional backplane-based electronic system typically includes a card cage, a backplane and multiple circuit board modules. The card cage typically defines a front opening, a back opening and a set of parallel slots leading between the front opening and the back opening. The backplane typically resides adjacent the back opening of the card cage.
During setup, a technician typically installs each circuit board module within the card cage. In particular, for each circuit board module, the technician slides that circuit board module through the front opening of the card cage and into a respective card cage slot. The technician typically pushes that circuit board module until a column of circuit board connectors along the leading edge of that circuit board module connects with a corresponding column of backplane connectors of the backplane.
When setup is complete, the circuit board modules reside within the card cage in a parallel manner. The parallel orientation of the circuit board modules alleviates the need for manufacturers to provide multiple air streams to the card cage in order to remove heat from the system. Rather, a manufacturer can design the system to use a single fan assembly that provides a single air stream through parallel spaces between the modules.
After setup is complete, the electronic system is ready for operation. At this point, the backplane provides a high density connection medium for carrying an assortment of signals to and from the circuit board modules. In particular, the backplane carries power supply signals from a power supply, or from a set of power buses, to each module. Additionally, the backplane carries data signals between the modules thus enabling the modules to communicate with each other to perform a variety of operations such as data processing operations, network interfacing operations, data storage operations, etc.
It should be understood that manufacturers of backplane-based electronic systems often attempt to squeeze the various system components into a very tight space. For example, such high-density designs enable manufacturers to market their products as compact systems which fit into relatively small footprints thus minimizing the amount of space needed at customer sites. Additionally, such designs may enable the manufacturer to reduce manufacturing costs since less materials are needed to make the smaller systems.
During the product lifecycle, manufacturers of backplane-based electronic systems may make enhancements to their initial designs. For example, using faster processing circuitry, a manufacturer may develop a faster circuit board module that performs the same operations as an older module but in less time, or the manufacturer may develop a new circuit board module that performs different and more-complex operations which are beyond the reasonable capabilities of the older module. The manufacturer may wish to offer modules having this faster processing circuitry to both its new customers, as well as its installed customer base in the form of an upgrade.
Since faster processing circuitry typically requires higher power, such faster processing circuitry often needs larger heat sinks to provide sufficient cooling. In some situations, due to the limited amount of space between columns of backplane connectors and due to the placement of the circuit board connectors of the circuit board modules, there may not be enough space between the circuit board modules to easily accommodate the larger heat sinks. There are a variety of conventional approaches to upgrading backplane-based electronic systems to use circuit board modules with larger heat sinks while preserving the use of the same backplane.
One conventional approach to upgrading a backplane-based electronic system to use a circuit board module with a larger heat sink while preserving the use of the same backplane (hereinafter called the module removal approach) is for the user to remove the circuit board module adjacent the circuit board module undergoing the upgrade, and then to replace the circuit board module undergoing the upgrade with a new circuit board module having the faster processing circuitry and the larger heat sink. In this approach, the user understands that the sacrifice for upgrading the existing module to the new circuit board module is the loss of the adjacent module.
Another approach to upgrading a backplane-based electronic system to use a circuit board module with a larger heat sink while preserving the use of the same backplane (hereinafter called the piggy-back approach) is for the user to replace two existing circuit board modules with a new primary/secondary circuit board module having a primary circuit board that supports a column of circuit board connectors, and a secondary circuit board that connects to the primary circuit board in a parallel manner. In this approach, the user essentially upgrades one of the existing circuit board modules by replacing that module with the primary circuit board. The user also preserves some of the functionality of the other existing circuit board module by replacing that module with the secondary circuit board. However, the user still loses the full connectivity provided by the two existing circuit board modules since the new primary/secondary circuit board module has only one column of circuit board connectors.